1. Field of the Invention
The present invention relates generally to memory apparatus for use in a data processing system and particularly to improved protection of rigid magnetic disc memory apparatus from particulate contamination originating from the area of the apparatus spindle bearings.
2. Description of the Prior Art
Magnetic disc drive memory apparatus usually have one or more rigid rotatable discs coated with a material which permits storage of data on and retrieval of data from the disc surface. To accomplish the "read" and "write" operations one or more recording heads are positioned adjacent to the disc surface. These heads "fly" on a thin layer of air generated by the rotating disc. Since the heads typically fly less than a micrometer above the disc surface, damage to the disc, the head, or both can result from particulate matter on the disc surface. Keeping the area surrounding the discs "clean" or free from particulate contamination has been a long standing problem in the field.
To minimize disc contamination, and thereby enhance reliability, discs are generally enclosed in substantially sealed housings which preclude the intrusion of ambient air. Air provided into the housing is passed through a filter designed to trap virtually all particles which could damage the disc or head before they enter the housing. This filter does not, however, solve the problem of particulate contamination of the discs in the housing caused by the spindle bearing. This bearing accommodates the shaft which functions to rotate the discs. Under high rotational speeds, contaminants, usually in the form of bearing lubricant mist, escape from the bearing. These contaminants typically migrate to the area surrounding the discs, where they can deposit and accumulate on the disc surface and eventually lead to "crashing", or contact of the read head with the particulates deposited on the disc surface. Crashing interferes with proper head operation and can lead to hardware damage.
To minimize contaminant migration into the disc area, magnetic disc apparatus commonly employ a "dynamic seal" between the area of the housing containing the discs and the spindle bearing. This dynamic seal is formed by a stator, or stationary member, and a rotor, a rotating member, adjacent thereto. During operation of the memory apparatus, a high pressure region results at the stator/rotor interface. This region discourages, but does not prevent, contaminant migration.
One method tried in the prior art to reduce mist contamination involves installation of a filter in the vicinity of the bearing. This results in a reduction of contaminants in the area of the discs, but does not provide adequate control.
Another prior art method is incorporation of a magnetic fluid seal between the rotor and stator. Because of the high rotational speed and large shaft diameter usually involved in a magnetic disc apparatus, this method is difficult to implement correctly.
The foregoing and other problems of the prior art are attended to by solutions described and embodied herein, as will be elaborated on hereinbelow.